1. Field of the Invention
This invention relates to a process for separating an isotope from a mixture of different isotopes by using a single laser beam.
2. Description of the Prior Art
Various processes for isotope separation are known, and several of these find commercial application. The best known processes are based on diffusion and are mainly used to separate uranium isotopes. However, these processes expend a great deal of energy, and only a few such plants exist. Another process is based on the use of centrifuges. This route seems industrially practicable, but the plant is mechanically extremely complicated. It is also known how to separate a gas flow of gaseous uranium hexafluoride by means of special nozzles, whereby the heavier isotopes are separated from the lighter ones.
The growing importance of the nuclear industry requires easy availability of separated or enriched isotopes, especially of uranium and also of hydrogen. A wide variety of isotopes is also needed in the area of scientific and biological research, for example isotopes of hydrogen, carbon, iron, and other elements. There exists, therefore, the need for a simple and easily executed procedure to separate isotopes. This procedure should be applicable to yield small as well as large quantities of separated isotopes.
During and after World War II, the development of photochemical processes for isotope separation was attempted. This did not succeed because suitable light sources were lacking.
More recently, consideration has been given to separating isotopes by using laser light, especially after the development of dye lasers made tunable laser light available. Nevertheless, no process has been brought to production maturity, because yields were quite small, so that economic and competitive execution was not possible.
In the conventional method for isotope separation by using laser beam, two or three photons with respectively different frequencies are used. In the two-step photoionization method using two photons with different frequencies, a first photon has a frequency for selectively exciting a particular isotope and a second photon has a frequency in the near ultraviolet or the ultraviolet region because the photon ionizes the excited isotope. That is to say, an excitation laser and an ionization laser are required. And moreover, since the ionization cross-section of an atom is smaller than that of an excitation cross-section by 10.sup.-3 -10.sup.-4, the intensity of the ionization laser beam must be larger than that of the excitation laser beam by 10.sup.3 -10.sup.4. In the three-step photoionization method using three photons with different frequencies, a first photon has a frequency for selectively exciting a particular isotope, a second photon has a frequency necessary for further exciting the excited isotope to a higher excited state and a third photon has a frequency necessary for ionizing the isotope excited in the higher state. Therefore, when the conventional methods are applied for uranium separation, three visible laser beams are required. And the constitution of the visible laser pumping light source and the control apparatus become extremely complex.
For the reasons stated above, the effective and simplified process for separating a particular isotope from a mixture of different isotopes wherein selective excitation and ionization of the particular isotope are made by a single laser beam.